Telemetering system



V. H. DSNEY TELEMETERING SYSTm v Julyze, w52

I- SV SheetsPSheet 1 Filed Aug. 8, 1945 Swan/ww@ VRGIL H. DISNEY @mi L A En u July 29, 1952 l Filed Aug. 8,1945

V. H. DISNEY myfamc sys-fm1 5 Sheets-Sheet 2 Vl RGIL. H. DISNEY July 29,1952 v. H. DISNEY- TELEHETERING s y'ls'vrm .5 Sheets-Sheet 4 Filed Aug. 8, 1945 smm- VIRCTIL' H. DISNEY .transmits through a number of Secretary of the Navy This invention relates in general to receiver circuits, end more particularly to a receiver cir cuit for 'operation :in a multi-channel radio flight test recorder.

In general the apparatus of which this invention is a part, consists of a multi-channel radio transmitter and receiver, so designed that, the transmitter may be placed in an airplane to be tested; to transmit :o the receiver. on the ground or in another plane, certain test dato such as a series of readings ci stresses in chosen members and the like.

The purpose of this invention is to develop a receiver for use with c. teiemetering system which independent channels from an airplane to ground or to another piane within a radius of approximately nity miles. Each channel is to be capable of carrying modulation "requencics up to about one hundred cycleshper second, such frequencies be ing obtained from bridge networks containing strain gages or other indicating instruments having similar output characteristics. The receiving equipment to be capable of receiving the chosen number of independent channels simultaneously, and recording the received information by means of arecordng oscillo'graph 0r other similar recorder.

A series of high frequency generators are mounted on a common shaft, to generate a series of signals of subcarrier frequencies. Each s nel of subcarrier frequency is modulated by a bridge circuit and amplified in a coupling tube. The outputs of the coupling tubes are mixed, amplied and utilized to modulate a radio transmitter.

At the receiving station .ie present invention consists of a synchronous motor dri'r'ng; a duplicate of the transmitters series of high frequency generators, each of which energizes one input of an electronic detecter or discriminator. Die other input of the electronic detector or discrrninator is energize-d from the receiver output. The output cf each electronic detecter go through a lov.' pass iter to an oscill graph element, where the modulations imposed on the correspoding frequency at the transmitter are faithfully reproduced.

It is an object of ...-s invention to produce a receiver for use in a telemeterin; system which transmits through e. number of independent channels from an airplane in Flight to ground or to another plane.

Another object is to produce an all electronic receiver. Y

i "rouwenf STATES Pa'llNl-` orrics A l .1 2,s05,34o .7 l

'TELEisIeTERrNG'sYs'rI-:M- .V l .l virgen. Disney, Elkhart, ma.. assignmu the".

United States of America as Application .august s, i945, serial No. 609,655

Another' Objectis to produce an electronic receiver that requires no moving parts.

Anoter object is to produce a receiver in which the subcarrier frequencies are obtained by division of a reference frequency.

Another object is the provision of a System which will be economical to manufacture, reliable in operation and which possesses all of the qualities of ruggecness and dependability in service.

In the drawings:

Figs. l and 2 illustrate in block diagram form one embodiment of this invention;

Fie. 3 ilustrares in block diagram form the'A receiver accordi?.n to the preferred. embodiment of this invention; an

Figs. 4c, 4b, and 1c taken together illustrate a circuit diagram of the receiver of Fig. 3,

In Fig. 1 is show: a generalized block diagram of the complete transmitter. The D. C. motor l used in the transmitting system. obtains its source of energy from tli'e ship's battery, not shown This more: is mechanically coupled to the phonic wheel generators 2. From these genrators voltages of :multiple frequency are derived and fed to the strain page modulators 3. In conjunction vcit: these voltages. a 500 cycle voltage is gen :etc-d for the purpose of synchronzing a motor at the receiver. This frequency is used as the pilot frequency. i ls signal along with the voilages obtained from the strain gage modulators is fed to a mixer 4 whose output in turn modulates a radio transmitter 5. The cornf ponents so described are those of the transmitter unit Installed in the piane being tested. The phonic '.vheei 2 may. if desired. generate signals of other frequencies than the ones indicated.

Fig, illustrates a complete block diagram'ot the receiver-recorder. A signal radiated from the transmite.- is intercepted cj-fe radio receiver 8' having associated therewith an automatic volume control l and pou-er amplifier units, not shown. The outpu: from the radio receiver is fed. to the AVC unit so that corstam. level signal output may be obtained. The out ut from the AVC unit is fed in c rt to a 50i; cycle filter 8 for the purpose of oot driving the 500 c; sjrnclaronolsI motor 9.

The en :gy from the lrer 8 is of such small magnitude that it L f cesser? to increase it by means of a tao-phase amplifier l0. This twophase ampler feeds the 50D cycle synchronous motor that is mecharically coupled to the receiver phonc wheel generators U; the frequency represented by the receiver.

. u output of which corresponds with the frequency output of the phonic wheel generators 2 of the transmitter. The output from each phonic vvheel in the receiver-recorder is fed to one particular discriminator l2 of thegroup generally designated- In addition to this, the complex Wave containing ,the intelligence from the plane is fed Afromrtbe AVC unit to each dis rl. inator l2.

A recording oscillogra'ph element I3, of the' group 'Iwheel generator of the receiver is connected to a. pbase sensitive unit- I4 along with the 500 cycle signal received from the plane inorder to maintain a'predetermined time 'relationship of the D. C. motor with respect'to .the 500 cycle synchronous motor. iff. A.' zl I Fig. 3 illustratesyja preferred Aembodiment of the receiver of this :invention in block diagram form. This receiver is adapted to be used with a transmitter transmitting two reference frequencies, such for example, as 500 and 20,000 cycles per second. The mixed signal containing the information of all of the channels and the two reference frequencies is picked up oy radio receiver l5 and delivered to the output, thereof insufficient strength for the subsequent apparatus. y

The two reference frequencies are filtered from a portion of the output by the first frequeny filter l5 and the second frequency lt-er l1. Preferably these reference frequencies are integral multiples and subrnultiples of all of the subcarrier frequencies utilized in the system. These' reference frequencies are cornoir d in phase setter I8 to hold the divided frequencies exactly in phase since the detect rs are sensitive to a. drift in phase. The output of the phase setter is controlled as to volume by automatic volume control I9 and amplified to the desired level by amplifier 2D before connection to the frequency dividers 2|, 26, which may operate at frequencies 0f, for example, 4,000 and 10,000 cycles respcctively. There are as many dividers as there are subcarrier channels, of which only two are illustrated in Fig. 3.

One subcarrier channel vvill be described by Way of example; and referring to Fig. 3 this channel will be that of the first divider. As above mentioned the first divider 2l takes its input from amplifier 20 and delivers an output Whose fundamental is the divided frequency, for example, 4,000 cycles/sec. This output is rich in harmonics, -and since the detector requires a sine Wave, the output passes through harmonic eliminator 22 before being amplified in amplifier 23, preparatory to its insertion into detector or discriminator 24. In this manner detector 24 at the receiver is supplied a subcarrer frequency that is an exact duplicate of the corresponding subcarrier at the transmitter. Detector 24 also receives an input of the complex Wave from the Hereinafter, the signal applied to the detector of the same frequency as the subcarrier signal generated at the transmitter, and utilized for obtaining dernodulation of the com lex signal, is referred to as the suppl d sub-carrier signal. The reaction of the supplied subcarricr signal upon the complex wave resolves the modulations placed on the subcarrier at the transmitter, said modulations in turn being recorded by recorder 25.

Referring to Figs. 4a, 4b, and 4c it has already been mentioned that it is necessary tf` *be operation of the detector units to have a. supplied I l generally designated, is connected to the output 1o `from each discn'minator.

subcarric r signal at the trarmitter in order to detect a particular subcarrier component in the complex wave containing the information sent down by radio from the plane. Inasmuch as the circuits are phase sensitive, it is imperative that the reference frequency utilized in the dividers for obtaining the supplied subcarrier signals be maintained at a constant p hase relationship` l ,with respect to all other signal components. This multi-charnel receiver system is fundamentally -in the detector circuits. proper phase relationships; between this referbased upon the principle that one reference frequency generated at `the transmitter be divided after reaching the receiver unit into proper integer submultiples for supplied lsuocarrier signals ence frequency, the sub-muitiple-frequency supplied subcarrier signals, and the components of subcarrier frequency in the complex wave carrying the information, it is necessary that the starting time for all the dividers to which the aforesaid reference frequency 'Ls applied be maintained for one particular phase relationship-for all signal'and signal components employed in tbe system. This starting characteristic is established by means of the circuit illustrated in block l0 and marked phase setter.

The frequencies generated at the transmitter consist of the aforementioned reference frequencies and the subcarrier frequencies which contain the desired information. Upon receiving these mixed signals at the receiver, the complex wave is passed through the tivo-band pass filters I5 and i7, Fig. 3, which separate the two refer ence frequencies of 500 and 20,000 cycles'from the complex vvave for insertion into the two corresponding input channels l and 2, Fig. 4a. The remaining subcarriers containing the information are injected in the output channel 3, Fig. 4c.

Referring nov: particularly to Fig. 4a, tube Vs is initially blocked from conducting by means of the high negative bias voltage imposed on the control grid by the voltage divider circuit com posed of resistors Rx, Rz, R: and R4. After the phase setting apparatus has warmed suiciently, the time delay relay 4 closes and connects the B+ voltage to the plate of the thyrathron V2. However, due to the fact that the rst reference frequency signal of 500 cycles connected to the control grid of tube V1 has been eliminated from the remainder of the circuit by setting variable resistor R5 at zero resistance, no signal current flows in the plate circuit of tube V1. Thus, the control grid of tube V: remains biased sufficiently negative to keep tube V2 from tripping. The bias voltage for V: is obtained by means of the voltage drop across resistor Re. The voltage drop acro resistor R1 is at this time not sucient to make tube V: ccnducting. However. at the desired time for operation the effective resistance of R5 is manually increased, thus introducing a signal in the control grid of V1 which correspondingly introduces a signal across potentiometer Rs of such a nature that the bias voltage on V2 is reduced toits critical firing voltage. This enables that tube to conduct and increase the current flow through resistors Rs and R: to the extent that the corresponding voltage drop across R1 is increased suciently to permit tube Va to oonduct. With this tube in operation, the second reference frequency of' 20,000 cycles is allowed to pass through this tube and develops a corresponding signal voltage across the plate resistor VIn 'maintaining the with the transmitter.

Upon. @ne 'introduction 0f uns vonage from .the V3 into the automatic volumecontrol, which comprises the tubes X74, Vs and Ys and associated components, Fig; 4a. a portion of. the signal after passing through variable mu tube: Vi'and V5 is introducedinto the'control grid of tube Ve ,which is a 'trlode-diode.

-this tube functions primarily to amplify as well The signal voltage obtained from, the plate resistor Rio i5 then The triode section of as phase invert the signal.

passed through the plate coupling condenser C1 or C2 depending upon the phase of the applied signal, and this circuit in turn is completed by passage of Ithe rectied current through resistors R11, R12, and either R13 Or R14. The Current passing through resistor Riz is then of a rectied nature and of proper phase relationship to produce a D. C. bias voltage in opposition to either an increase or decrease of signal input, It might be further pointed out that a more delayed automatic volume control action can be obtained by paralleling a condenser across the resistor R12.

This constant level signal is then applied to amplifier 2G, containing tube V7 and associated components, Fig. 4b, and is amplified to a level sufficient for injection into the divider circuits.

In the frequency divider 2i, the reference irequency of 20,000 cycles'is divided to the repetition frequency of the particular subcarrier, for example, 4000 cycles. used most commonly as frequency dividers were oscillatory circuits having la natural period somewhat longer than that of the frequency desired at the output of the divider. The input wave whose frequency veas to be divided, acted to cause the oscillatory circuit to start a new cycle of operation after a given number of cycles of the original wave has elapsed. Such divider civ-:cuits use gaseous discharge tubes, multivibrator stages. or blocking oscillators.

In some applications the dividers of the prior art were not satisfactory because of inability due to fluctuations in supply voltages, or due to changes in tube characteristics. This was especially true if the divisor was large. They were particularly troublesome if the input frequency was not fixed, for if the input frequency' varied an appreciable amount the divider circuit Would become unstable or would divide by a different amount than was desired.

The frequency divider of this invention, Fig. 4b, is extremely stable for counts up to sixteen and higher, and the input frequency. can be varied over a ten to one range or more without changing the count or divisor.

The counter circuit counts a given number of pulses without regard to their frequency and res to produce a single pulseafter the required number of pulses have occurred. The counting is accomplished by charging a condenser in a stairstep fashion. 4

The voltage across this condenser is applied to a trigger circuit that trips at a predetermined voltage level. Upon tripping. the trigger circuit in a very brief inter-"al of time discharges the condenser, creates an impulse which ser-ves as the output voltage from the divider, and prepares itself to stand by until :he condenser voltage again reaches the critical value. For every cycle of the input frequency one step is pro- Until recently the circuits t' duced and the number of steps that will occur .before the trigger circuit trips will depend upon 4the size of the risers on these steps and upon the cri tical voltage of the trigger circuit. The length tion of the trigger circuiti I-or best: results the input wave to the counter n Y* circuit should-be of rectangular form. This is generally accomplished, in the aforementioned amplien-v'hich in this case would be a square AWave amplifier. V'Ih'evoltage from the square v Wave amplifier is applied to the series combination of the condensers C: and C4, and theV diode Ve. W'hen the square wave amplifier output is changing in the positive direction. acharging current flow: through this series `cornbination.

This current charges the condensers so that the peak voltage is divided betweenthem inverselyl as `their respective capacitanccs. C: is usually small compared to C4 so that the voltage across C4 will be small compared to the peak value of the applied signal. This action produces the riser on the first step in the stairstep voltage across C4.

As vv'as stated before, the number of steps that will occur before the trigger circuit trips depends upon the size of the risers on these steps and he critical voltage of the trigger circuit. The si :e of the risers will depend upon the peak; to

,i paal: value of the rectangular voltage wave and the ratio of C3 to Ci. The critical voltage of the trigger circuit depends upon the bias on the trigger tube. Therefore, for a given square Wave amplier operation Ca or C4 may be adiusted to change the count or divisor of the circuit, or the bias on the trigger tube may be changed. In some cases it will be found desirable to make C3 adjustable to give large changes in count and a bias adjustment. can be used for minor adjustment or calibration.

The trigger tube V9 shown in the divider, Fig. 4b, may be in the same envelope with the output amplifier tube. It isAof the blocking oscillator type, and it may be of the multivibrator type. The grid of the trigger tube has no D. C. pat-h to ground except what may be present in the form of leakage resistance, so the trigger tube is not self-oscillatory except over long periods of time due to leakage resistance. The choice of value in C.; .vill determine the time constant for the particular leakage resistance and will limit the low frequency output of the frequency divider. The period of oscillation may readily be in the order of l5 seconds and is of no partlcular concern except vrherc very low frequencies are involved. Ii the time constant of this circuit is too low for the frequencies involved it will show up in the stair-step volta-ge wave across C4 by a downward slant of the treads on the steps. The downward slope becomes increasingly large as the number of steps is increased so that there is a tendency toward instability for large counts as the net gain for a given step high on the stairs will be small because of a loss of voltage the tread. This nearly equals or may exceed the rise in voltage on the riser. Such a condition is easily diagnosed with an oscillosc pe. For best results the tread should be horizontal and the risers nearly vertical. 1n order that the risers may be nearly vertical the time constant of the circuit in which C: and C4 are charged must be considered. The effective resistance-capacity of this circuit should be so loiv that the time constant is negligible compared to the time of a period 1/f. If this time constant riod of the output of the frequency dividerv would, therefore, be variable Whichais not strictly an integral submultiple of the input. l

livl taking the proper precautions it 1s possible l tomake the divitnng factor ofttie'rrequency divider quite llarge, that is, somethingin the order of'6l. Ordinarily, a. count of 8 `or l5'is as high as it is usually desirable Ato go ,with one stage of division, especially since it is so easy to cascade divider circuits andthereby multiply the Y counter dividing number. Y

A jacl: 3 is connected into the output circuit of the divider circuit for testing purposes.

As previously pointed out, it is desirable to apply a sine wave to theydetector unit. Inasrnuch as the Wave from the divider circuit contains many harmonics, the sine wave is obtained bypassing the complex signal through the Harrnonic ElLninator 22, which may comprise the L-C netrvorl; shown, Fig. 4h, or a low pass lter vvhose cut-ofi characteristic is between the first and second harmonic. upon leaving the harmonic eliminator is too 10W for operation in the detector unit, and it is necessary at this tirne to increase the level of the signal hy passing it through amplifier 23, which may comprise the circuit of tube Vio and associated components, Fig. 4b. This supplied subcarrier sional is then applied by Way of lead C to the detector across resistor-R15, Fig. 4c, and the complex wave containing the information on the subcarrier frequency is then applied to the detector through the coupling transformer T1, to the control grids of the detector tubes Vn and Vie. The functioning of the detector is such that'l the information contained in the subcarrier frequency corresponding to the frequency obtained from the divider unit appears in the output of tubes Vu and V12, and it is indicated on the 500 micro-ampere instrument, and recorded in the recorder unit. Filters may be pro-` vided, if desired, between tubes V11 and Viz and the recorders.

Exemplary values for the circuit elements are given in the following table:

A more detailed disclosure of a suitable detector '.s found in application Ser. No. 593,605, Virgil H. Disney, filed May 14, 1945, for Discriminator Circuit.

"bviously many modifications and variations The level of the signal,

of the present invention are possible in the light of the above teachings. It is therefore to be understood that Within the scope of the appended claims the invention may be practiced otherwise than as specicaliy described.

What is claimed is:

1. Receiver apparatus for use in a telemetering `system of the type in which a radio Wave-anda 'plurality of A.-C. signals are generatedfat a 'transmitter station, two of.said signals being of;

`trvo 'reference frequencies respectively. other of said signals being subcarrier signals of suhcarrier frequencies respectively, said subcarrier signalsY being modulated in accordance vwith variations in aplurality of quantities to be' measured respectively thereby. to provide a plurality of subcarrier signals having a pluralit;Y or modulation compi-4 nents respectively, all said signals being utilized to modulate said radio wave,` said receiving apparatils comprising radio receiving means adapted to receive said Wave and to supply a complex A.C. receiver signal containing all said reference and subcarrier frequencies and said variations as components thereof, filter means operatively connect-ed to said receivingy means for 0btaining from the receiver ence signals of said tivo reference frequencies respectively, phase setter means operatively con- 'if-:cted to said filter means, amplifier means energized from said phase setter means, said phase setter means using cons ructed and arranged for utilizing one of said reference signals to control the phase of the other of said reference signals, .said other reference signal being applied to said 'impl/ine;- rneans in predetermined phase relationship to said complex A.C. sif'nal, a plurality of frequency divider means energized from 'said amplier means, sai plurality of frequency divider means each including a counter circuit and being constructed and arranged to provide a plurality of supplied subcarrier signals of frequencies corresponding respectively to the frequencies of the subcarrier signals at the transmitter station, a plurality of discriminate: means, each of sold discriminator Ineens including a pair of similar electron discharge amplifier tubes each having a control grid, said pair of electron discharge tubes having one of said supplied subcarricr signals applied to said control grids in phase, said complex wave being applied to said control grids in phase opposition, said plurality of discriminator :ncans being. constructed and arranged to separate the plurality of modulation components respectively from the complex signal, and a plurality of indicating means'opcrativcly connected to said plurality of discriznlnator :ne-ans respectively and constructed and arranged to indicate variations in said modulation components.

2. Receiver apparatus for use in a telemetering system of tlze type ur which a radio wave and a plurality of .'e .-C. signals are generated at n. transmitter station, two of said signals being of tivo reference frequencies respectively, other of said signals being suhcarrier signals of subcarrier frequencies respectively, said succarrier si als being modulated in-accordance with variations in a plurality of quantities to be measured respecively thereby to provide a plurality of suboarrier signals having a pluralitj.1 of modulation componcnts re. pectizely, all said signals bring utilized to modulate said rudio wave, said receiver apparates comprising radio receiving means adapted to receive said wave and to supply a complex A.C. receiver signal containing al1 said refersignal tivo A.C. reference and'V subcarrierfrequencies and said varations as components thereof, filter means oper'- atively connected to said receiving means for obtaining from the receiver signal two s-C. 'reference signals -of said two reference frequencies operatively connected to said last named means and to said receiver means for utilizing said pluiralty of supplied -subcarrier signals for separatrespectively, phase setter means operatively con'- neet-ed to said filter means, amplifier mears ener- 'gized from said phase settermeans, saidphase setter means being constructed and arranged for utilizing one o1 said reference signals to control the phase of the other-:of said reference signals,

said other reference signal being appliedzto saidv ampliner means in predetermined phaserelationship to said complex Afcfsignal, a. plurality of frequency divider means energized from said amplifier means, said pluralityof `frequency divider means each including a counter circuit and being constructed andv arranged to provide a plurality of supplied subcarrier signals of frequencies cor- -respondingr respectively to the frequencies of the subcarrier signals at the transmitter station, a plurality of discriminator means, each of said discriminator means including a pair of similar electron discharge amplifier tubes each having a control grid, anode, and cathode, said cathodes being constructed and arranged to separate said plurality of modulation components respectively from said complex signal, each of said indicator means being adapted to indicate variations in a different one of said plurality of modulation components.

3. Receiver apparatus for use in a telemet-ering vsystem of the type in which a radio wave and a plurality of A.-C. signals are generated at a transmitter station, tvvo of said signals being of two reference frequencies respectively, other of said signals being subcarrier signals of subcarrier frequencies respectively. said signals of Lubcarrier frequencies being modulated in accordance with variations in a plurality of quantities to be measured respectively thereby to provide subcarrier signals having a plurality of modulation components respectively, all said signals beingutilized to modulate said radio wave, said receiving apparatus comprising radio receiving means adapted to receive said wave and to supply a. complex A.C. receiver signal containing all said reference and subcarrier frequencies and said variations as components thereof, filter means operatively connected to said receiving means for obtaining from the receiver signal two A.-C. reference signals of said two reference frequencies respectively, phase setter means operatively connected to said filter means, amplifier means eriergized from said phase setter means, said phase setter means being constructed and arranged for utilizing one of said reference signals to control the 'phase of the other of said reference signals, said other reference signal being applied to said amplifier means in predetermined time relationship to said complex A.C. signal, a plurality of frequency divider means energized from said amplier means, said plurality of frequency divider means each including a counter circuit and being constructed and arranged to provide a plurality oi supplied subcarrier signals of frequencies corresponding respectively to the subca'rrier frequencles at the transmitter, a plurality of means i a plurality of quantities to be measured thereby.`

ing-said plurality of modulation components rcspectively, and a plurality of recording means operatively connected to said last, named meanS respectively for recording variations in said modulation components respectively,v

4. Receive: apparatus for use in a telemetering system of the type in which aradio Wave and a ,plurality of A.-'C. signals are generated at'fa transmitter stsliomtwo of. said signals being o f two reference frequencies respectively, other of said signals beingsubcarrier signals 'of subcarrier frequencies ,respectively said. subcarrier signals being modulated in accordance With'variations in to provide a plurality of subcarrier signals having ,a plurality of modulation components respectively, all said signals being utilized to modulate said radio wave, said receiving ,apparatus comprising radio recevinfy means for receiving said wave and adapted to supply a complex A.'C. receiver signal containing all said reference and subcarrier frequencies and said variations as components thereof, filter means operatively connected to said receiving means for obtaining from the receiver signal tivo A.-C. reference signals of said tivo reference frequencies respectively, phase sette'. means operatively connected to said lter means to be energized therefrom, amplifier means energized from said phase setter means, said phase sett-er means being constructed and arranged for utilizing one of said reference signals to control the phase of the other of said reference signals, said other reference signal being applied to said amplifier means in predetermined' phase relationship to said complex A.C. signal, a plurality of frequency divider means energized from said amplifier means and adapted to provide a plurality of supplied subcarrier signals of frequencies corresponding respectively to the frequencies of the subcarrier signals at the transmitter station, a plurality of discriminator means having said complex receiver signal applied thereto and said plurality of supplied subcarrier signais applied thereto respectively, said discriminator means being constructed and arranged to separate said modulation components respectively from the complex signal, and a plurality of indicating means operatively connected to said plurality of discriminator means respectively and constructed and arranged to indicate variations in said modulation components.

5. Receiver apparatus for use in a telemeteririg system of the type in which a radio Wave and a."

plurality of A.C. signals are generated at a transmitter station. two of said signals being of two reference frequencies respectively, other of said signals being signals of s ubcarrier frequenciesk respectively, said subcarrier signals being modulated in accordance with variations in a plurality of quantities to be measured respectively thereby to provide a plurality of subcarrier signals having a plurality of modulation components respectively, all of said signals being utilized to modulate said radio wave, said receiving apparatus comprising radio receiving means adapted to receive said `:rave and supply a complex A.-C. receiver ignal containing all said reference and subcarri'er frequencies and said variations as components thereof, band-pass filter means operatively connected to said receiving means for obtaining from the receiver signal two A.C. ref-v two electron discharge tube means having said two reference signals applied thereto respectively,

. one of said electron discharge tube means being adapted to control the instan-tkvhen the-other discharge. tube means becomes operative thereby toc'ontrol the phase of the referencev signalapplied to said amplifier means, va plurality of frequency divider means energized from said amplifier means: each of said divider means including means for counting the cycles ofsaid last named reference signal'and generating a supplied subcarrier signal having a frequency which is an integral submultiple of thefiequency of tne last named reference signal, a plurality of means 1ncluding L.C. networks for eliminating undesirable harmonic and su'bharmonic components from the supplied subcarrier signals respectively, a plurality of discriminator mear having said complex receiver signal applied thereto and said supplied subcarrier signals applied thereto respectively, said discriminator means being constructed and arranged to separate said modulation components respectively from the complex signal, and a plurality of indicating means operatively connected to said plurality of discriiA inator means respectively and constructed and arranged to indicate variations in said modulation components. 4

6. Receiver apparatus for use in a telemetering system of the type in which a radio wave and being modulated in accordance with variations in a plurality of quantities to be measured respectively thereby to provide a plurality of subcarrier signals having a plurality of modulation components respectively, all said signals being utilized to modulate said radio wave, said receiv ing apparatus comprising radio receiving means adaptedto receive said wave and to supply a complex A.C. receiver signal containing all said reference and subcarrier frequencies and said variations as components thereof, filter means operatively connected to said receiving means for obtaining from the receiver signal two A.C. reference signals of said two reference frequencies respectively, phase setter means operatively connected to said lter means, said phase setter means including a pair of electron discharge tube amplifiers connected to be energized by said pair of rei'erence signals respectively, one of said amplifiers being adapted to control the operation of the other, the other of said amplifiers having the higher frequency of said reference signals applied thereto, amplifier means energized by the signal from said other amplifier, a plurality of frequency divider means energized from said amplifier means, each of said plurality of divider l2 means including a counter circuit and adapted to provide a supplied subcarrier signal of a frequency corresponding to a different one of the vsubcarrier signals at the transmitter, a: plurality of discriminatcr means having said complex re- .ceiver signal applied thereto and the supplied subcarrier signals applied thereto respectiveLv, said plurality of discriminate: means being con.-

'structedand arranged to separate said plurality .of modulation components respectively'from the complex'signal. and a plurality of indicating means operatively connected .to said plurality of dlscriminator means respectively and constructed and arranged to indicate variations in said plurality of modulation components.

I 7. Receiver apparatus for use in a telerneten-v ing system of the type -invhich a radio wave and a plurality of A.C. signals are generated at a transmitter station, two of said signals being of tvvo reference frequencies respectively, other of said signals being subcarrier signals of subcarrier having a plurality of modulation components respectively, all said signals being utilized to modulate said radio Wave, said receiver apparatus comprising radio receiving mea-ns adapted to receive said wave and to supply a complex A.C. receiver signal containing all said reference and subcarrier frequencies and said variations as components thereof, filter means operatively eonnected to said receiving means for obtaining from tne receiver signal two A.C. reference signals of said two reference frequencies respectively, means operatively connected to said filter means for utilizing said reference signals to obtain a plurality of supplied subcarrier signals having frequencies corresponding respectively to the frequencies of the subcarrier signals a plurality of discriminator means having said plurality of supplied subcarrier signals applied thereto respectively, all said plurality of discriminator means having said complex receiver vsignal applied thereto, said plurality of discrim- VTRGIL H. DISNEY.

REFERENCES CITED The following references are of record me of this patent: m the UNITED STATES PATENTS Number Name Date 1,562,965 Horton Nov. 24, 1925 1,577,722 Horton -Mar. 23, 1926 2,426,778 Long Sept, 2, 1942 

